Extensive research to produce oriented nonlinear optical (NLO) chromophores exhibiting large electro-optic (EO) activity and good thermal stability has been pursued for years. Recent studies showed that effective site isolation and molecular assembly are critical for improving the performance of such materials. In newly reported dendritic molecular glasses, chromophores with large hyperpolarizability (βμ) are selectively functionalized and self-assembled into well-defined architectures, leading to materials with high poling-induced acentric order and large EO coefficients (r33 values of up to 100-300 pm/V at the wavelength of 1310 nm). These materials provides an effective platform to build innovative optical devices, such as low-Vπ Mach-Zender interferometers, EO ring resonators, and polymer-silicon slotted waveguide modulators. Although the progress is encouraging, it is believed that greater impact could be accomplished for high-speed information processing if the well-established semiconductor processes for microelectronics could be applied to photonics. High speed processing will provide a boost to the development of devices for urgently needed high bandwidth information processing. In order to fulfill this, materials need to meet numerous stringent requirements in manufacturing, assembly, and end-use environments of devices. Therefore, the search for organic E-O materials with sufficient r33 values and excellent thermal stability is an ongoing challenge.
The poling induced polar order of large βμ chromophores in any organic spin-on materials must withstand prolonged operation temperatures of up to 100° C., and brief temperature excursions during processing that may exceed 250° C. To date, many studies have been performed on improving one or some of these required properties. However, none of the materials developed to date meet all of the above criteria. Furthermore, the thermal stability and decomposition mechanisms of new generation of highly polarizable chromophores are not well understood.
The intrinsic stability of typical high-r33 E-O dendrimers and binary polymers under high temperature (up to 200° C.) has been investigated. These materials often contain high concentrations of chemically sensitive chromophores, which are spaced apart by either physical π-π interactions or “loosely” crosslinked polymeric networks containing flexible tether groups. Most of these materials have relatively low to moderate glass transition temperatures (Tg), and are only thermally stable enough (85-150° C.) to satisfy the basic fabrication and operation of conventional optical modulators.
However, rapid decomposition of chromophores is often observed for these materials under higher temperatures. From both thermal and spectroscopic analysis of a standardized dipolar chromophore, 2-[4-(2-{5-[2-(4-{bis-[2-(tert-butyl-dimethyl-silanyloxy)-ethyl]-amino}-phenyl)-vinyl]-thiophen-2-yl}-vinyl)-3-cyano-5-methyl-5-trifluoromethyl-5H-furan-2-ylidene]malononitrile (AJL8), it was found that a bimolecular reaction mechanism is responsible for the initial decomposition of the chromophore. The detailed mechanism for site-specific reactivity of NLO chromophores has not been well understood, and therefore optimization of organic E-O materials for high temperature applications has been impaired.
A need exists for E-O materials with acceptable r33 values that also have thermal stability sufficient for manufacturing, assembly, and end-use environments of electro-optic devices. The present invention seeks to fulfill this need and provides further related advantages.